Lettuce necrotic yellows

Cause

Lettuce necrotic yellows virus (Rhabdovirus).

Symptoms

Initial symptoms are a browning of leaf veins, followed by partial death of the inner leaves. Affected plants are yellow and stunted, often with twisted and lopsided leaves. In advanced stages, the outer leaves wilt severely, giving the plant a flattened, stunted appearance.

How it spreads

The weed common sowthistle (Sonchus oleraceus) is the major host of both the virus and the sowthistle aphid (Hyperomyzus lactucae), which spreads the virus in a persistent and propagative manner. This aphid is the major carrier (vector) of the virus and is often found in large numbers on the flower stalks of sowthistle.

Outbreaks of necrotic yellows are usually associated with infected sowthistles within or near lettuce crops. The sowthistle aphid does not breed on lettuce, and there is little plant-to-plant spread of the virus in lettuce crops.

Crops affected

Necrotic yellows is a common disease that can cause serious sporadic losses in lettuce crops.

Control

Destroy sowthistle weeds in and around the crop. Maintain aphid control in crops.

Chemical registrations and permits

Check the Australian Pesticides and Veterinary Medicines Authority database for chemicals registered or approved under permit to treat this pest on the target crop in your location. Always read the label and observe withholding periods.